Drill head assembly

ABSTRACT

An impact rock drilling tool is provided with a removable head assembly and an anvil which receives percussive and rotational loads. The anvil and head assembly are threaded together to hold the head assembly on the anvil. The anvil has a radially outer shoulder surface which opposes a radially outer impact surface on the head assembly. The anvil also has an end surface which opposes a radially inner impact surface on the head assembly. Deformable washers are interposed between the impact surfaces of the head assembly and the opposed surfaces on the shoulder and end of the anvil respectively. The deformable members uniformly distribute the load across the entire surfaces and thus increase the effective bearing surfaces for transmitting the load between the anvil and the head assembly.

[ Feb. 12, 1974 United States Patent [1 1 Pearson DRILL HEAD ASSEMBLY Primary ExaminerMarvin A. Champion Assistant ExaminerWilliam F. Pate, Ill

[.75] Inventor: Bernard A. Pearson, Bothell, Wash.

[73] Assignee: Smith-Williston, Inc., Seattle, Wash.

Nov. 3, 1972 [22] Filed:

An impact rock drilling tool is provided with a remov- [21] Appl. No.: 303,328 able head assembly and an anvil which receives percussive and rotational loads. The anvil and head assembly are threaded together to hold the head assembly on the anvil. The anvil has a radially outer shoulder surface which opposes a radially outer impact surface on the head assembly. The anvil also has an end surface which opposes a radially inner impact surface 56 om n /-J n 8 2B 1 1 3 2 O lDEL 5 l 3 ,2 7 00; 23 4 0 ,l m W. 3 90 7 34 l 7., .1] u .9 m w s a 9 m2 H r H w? m S1 L C [00 W l l l ll. 2 8 5 55 .lIl

on the head assembly. Deformable washers are interposed between the impact surfaces of the head assembly and the opposed surfaces on the shoulder and end of the anvil respectively. The deformable members 287/103 D uniformly distribute the load across the entire surfaces 173/131 and thus increase the effective bearing surfaces for 173/131 X transmitting the load between the anvil and the head assembly.

5 Claims, 2 Drawing Figures 1,428,415 Brossoit 2,005,564 Schalscha 2,597,574 Dickenson DRILL HEAD ASSEMBLY CROSS REFERENCETO RELATED APPLICATION This application discloses subject matter shown in my copending application Ser. No. 232,695, filed Mar. 8, 1972.

BACKGROUND OF THE INVENTION I III'C.

SUMMARY THE INVENTION It is an object of this invention to provide means for securing a head assembly to an'anvil of an impact drilling tool which allows the head assembly to receive extreme torque and percussive impact loads without fail- It is another object of this invention to distribute the impact loading between an anvil and a drill head assembly over the widest possible area. Basically, these objects are obtained by providing an anvil with multiple impact surfaces, providing the head assembly with impact surfaces confronting those of the anvil, and placing between each confronting set of impact surfaces a deformable member. The deformable member becomes compressed under the loading to fill all of the voids, microscopic irregularities or machining errors in the impact surfaces of the anvil and the head assembly so that the impact loading is borne by theentire surface area of the available impact surfaces. In this manner distribution of the shock wave of the percussive loading occurs over a larger surface area than heretofore possible and a substantial portion of the impact loading is transmitted from the radially inner end surface of the anvil to the head. assembly where shock transfer is most effective.

BRIEF DESCRIPTION OF THE FIGURES OF THE DRAWING FIG. I is an axial section of an anvil and rock drill head assembly embodying the principles of the invention.

FIG. 2 is a modified form of an anvil and rock drill head assembly also embodying the principles ofthe invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As best shown in FIG. 1 an anvil is provided with a threaded interconnection of 12 of the type illustrated in said co-pending patent application in which the threads have a tight engagement at a point a and a gap at point b. The anvil is provided with a radially outer shoulder having an impact surface 16 and a radially inner end having an impact surface 18. An air passage 20 is provided for introducing a pressurized stream of air into the head assembly for clearing broken bits of rock or soil or the like from the forward end of the head assembly.

The head assembly 14 is provided with corresponding air passages 22 and a plurality of carbide bits or buttons 24. the bits can be of conventional construction or, if preferred, can be of the type illustrated in said copending application Ser. No. 232,695.

Due to the threaded interconnection 12, and the percussive and rotary loads placed on the anvil and head assembly, the threads 12 normally tend to tighten during operation of the drilling tool. In order to reduce this tightening the loading is more uniformly distributed in this invention thus increasing the loading to which the tool can be subjected. The head assembly is also provided with impact or bearing surfaces. One of which is a radially outer impact surface 30 opposed to the anvil impact surface 16 and the other is a radially inner impact surface 44 opposing the anvil end surface 18. Interposed between the surfaces 16 and 30 is a deformable washer 40 preferably of cold rolled steel that .upon subjection of the loading will deform to fill all of the irregularities in the surfaces to which it abuts so that the entire surfaces of the impact surface 16 and impact surface 30 are utilized for transmitting the load. Similarly a second washer 32 of cold.rolled steel is used to uniformly distribute the load over the entire surfaces 18 and 44.

The advantages of the use of these deformable members or washers are that irregularities in each of the surfaces used for transmitting the loads can be compensated for so that the loading is distributed over the entire surfaces rather than isolated points on those surfaces. Secondly, since it is difficult, if not impossible, to machine all of the surfaces 16, 30, 18 and 44 to match perfectly for distributing loads, the deformable washers allow a mating between both the radially outer surfaces and the radially inner surfaces so that both sets of surfaces are utilized in distributing the loads. Thus not only is the bearing surface for distributing loads increased, thus decreasing localized stresses in the anvil or head assembly, but also the shock wave of the loading is permitted to travel straight up the anvil directly into the head assembly close to the axial center of the head assembly. This portion of the head assembly has the highest strength and is best able to withstand the shock wave thus prolonging the useful life of the head assembly. I

FIG. 2 illustrates a modified embodiment of the anvil and head assembly. An anvil is provided with an air passage 62, a radially outer impact surface 64 and a radially inner impact surface 66 on the end of the anvil. The head assembly 68 is provided with a radially outer irripact surface 70 opposed to the impact surface 64 and a radially inner impact surface 72 opposed to the impact surface 66. Corresponding air passages 74 are provided in alignment with the air passage 62. A conventional standard J thread removably secures the head assembly to the anvil. Interposed between the impact surfaces 64 and 70 is an annular deformable washer 80. Correspondingly, a second washer or deformable member 82 is provided between the impact surfaces 66 and 72. The function and operation of the impact surfaces and deformable members is the same as that described for the preferred embodiment of FIG. 1 and further explanation is not believed necessary. The advantage of this embodiment is that it achieves the simplicity of standard thread design with the added load capability.

While the preferred forms of the embodiment have been illustrated and described, it should be understood that variations and modifications will be apparent to one skilled in the art without departing from the principles of the invention. Accordingly, the invention is not intended to be limited to the specific forms described.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A rock drilling tool having an anvil and a head assembly, means threadably securing the head assembly to said anvil, first and second sets of impact surface means respectively confronting one another on said anvil and head assembly, the first and second deformable members interposed between each set of said impact surface means for providing full uniform contact between each set of impact surfaces so as to increase the impact bearing surface of the head assembly and anvil.

2. The combination of claim 1 said first set of impact surfaces including a radially outer shoulder surface on said anvil opposed to an annular radially outer surface on said head assembly, said second set of impact surfaces including an end surface on said anvil opposed to a radially inner surface on said head assembly, and said deformable members each including a cold rolled steel washer positioned respectively between the entire opposed surfaces of said anvil shoulder surface and head assembly radially outer surface and said anvil end sur face and head assembly radially inner surface.

3. The combination of claim 2 said threadably securing means including an external thread on said anvil and an interval thread on said head assembly, said threads having a variance for producing normal thread engagement toward the axially inner end of the anvil and a gap between the threads toward the axially outer end of said anvil.

4. The combination of claim 2 said threadably securing means including a standard thread externally positioned on the anvil and interconnected with an internally positioned standard thread on the head assembly.

5. A rock drilling tool having an anvil, a head assembly removably secured to said anvil, and means for guiding air through said head assembly, the improvement comprising;

a radially outer shoulder impact surface on said anvil,

a radially inner impact surface on said head assembly opposed to said anvil shoulder impact surface, an end impact surface on said anvil, a second impact surface on said head assembly opposed to said anvil end impact surface, and first and second deformable impact transferring means interposed respectively between said first impact surface and said shoulder impact surface, and said second impact surface and said anvil end impact surface for spreading the impact loads uniformly over said impact surfaces. 

1. A rock drilling tool having an anvil and a head assembly, means threadably securing the head assembly to said anvil, first and second sets of impact surface means respectively confronting one another on said anvil and head assembly, the first and second deformable members interposed between each set of said impact surface means for providing full uniform contact between each set of impact surfaces so as to increase the impact bearing surface of the head assembly and anvil.
 2. The combination of claim 1 said first set of impact surfaces including a radially outer shoulder surface on said anvil opposed to an annular radially outer surface on said head assembly, said second set of impact surfaces including an end surface on said anvil opposed to a radially inner surface on said head assembly, and said deformable members each including a cold rolled steel washer positioned respectively between the entire opposed surfaces of said anvil shoulder surface and head assembly radially outer surface and said anvil end surface and head assembly radially inner surface.
 3. The combination of claim 2 said threadably securing means including an external thread on said anvil and an interval thread on said head assembly, said threads having a variance for producing normal thread engagement toward the axially inner end of the anvil and a gap between the threads toward the axially outer end of said anvil.
 4. The combination of claim 2 said threadably securing means including a standard thread externally positioned on the anvil and interconnected with an internally positioned standard thread on the head assembly.
 5. A rock drilling tool having an anvil, a head assembly removably secured to said anvil, and means for guiding air through said head assembly, the improvement comprising; a radially outer shoulder impact surface on said anvil, a radially inner impact surface on said head assembly opposed to said anvil shoulder impact surface, an end impact surface on said anvil, a second impact surface on said head assembly opposed to said anvil end impact surface, and first and second deformable impact transferring means interposed respectively between said first impact surface and said shoulder impact surface, and said second impact surface and said anvil end impact surface for spreading the impact loads uniformly over said impact surfaces. 